Yes, wildlife contraception works

When my 12-year-old son encounters any phenomenon that doesn’t yet fit into his worldview, he’ll sometimes ask, “Dad, is that a ‘thing,’” meaning, is it something worth caring about?

This isn’t just my son’s problem, of course; at times we all face bewildering novelty. And if it’s a thing like a new technology that makes us confront our deeply rooted feelings about nature, we might find ourselves turning away from it.

I wonder if that’s why the idea of wildlife contraception has not -- except as a curiosity -- entered the public conversation. Wildlife contraception isn’t new. Wildlife biologists were injecting deer with steroids to control fertility in the 1960s, but the steroids passed easily into the food chain and caused all sorts of side effects in wildlife. Now we use immunocontraceptives, protein-based vaccines that are reversible and cannot enter the food chain. They cause no harmful side effects in treated animals.

Several immunocontraceptive vaccines have been tested and proven effective in the field. Among the best-tested is PZP, which is produced by my colleagues at the Science and Conservation Center in Billings, Montana. Antibodies produced in response to PZP prevent pregnancy by blocking sperm from attaching to eggs. It is delivered to mares, does or other female animals by hand-injection or by darting, and a single treatment lasts one to three years. Boosters last even longer.

But here’s the puzzle: Why aren’t these vaccines used more? Fertility control entered the domain of wildlife management 20 years ago, when the National Park Service began employing PZP as its principal tool for managing the historic population of wild horses at Assateague Island National Seashore in Maryland.

The Park Service has managed horses at Assateague with PZP ever since. Horse population targets have been met, revised downward, and met again. For 20 years!

If Assateague stood alone, it could be ignored. But it has lots of company. The use of PZP for population control has spread down the East Coast to three other wild horse herds. It works in the West, helping to manage wild horses in seven Bureau of Land Management or Forest Service herd-management areas, seven wild horse sanctuaries, and five Native American reservations.

Nor is fertility control limited to wild horses. Populations of suburban white-tailed deer on the East Coast have been stabilized or substantially reduced in three communities with the help of PZP. Reproduction in the bison herd on Santa Catalina Island, California, was stopped cold -- in two years -- with PZP, ending the expensive process of controlling populations by shipping bison off the island.

Yet that is a small drop in the giant bucket of human-wildlife conflicts. The BLM, for example, treats an average of 500 mares a year in a free-roaming population that is now approaching 50,000. The BLM’s excuse boils down to, “It’s too hard.” (By comparison, should we consider it “easy” to spend $45,000 apiece to provide lifetime care for the 50,000 captive “excess” horses that the BLM now holds?)

So why hasn’t wildlife contraception become a “thing?” For some people, it has. Those in the animal shelter and rescue community, for example, eagerly embrace wildlife contraception as but a short hop from the spaying and neutering of cats and dogs. Wildlife contraception is also a thing for those paid to control so-called nuisance wildlife, mostly in response to consumer demand for non-lethal solutions.

For many people, though, especially those in the conservation community, “wildlife contraception” links two terms that bear non-overlapping sets of associations. Depending on your philosophy, wildlife runs free, protected and separate from the human community; or it is a natural resource to be conserved and sustainably used for human benefit. In contrast, contraception evokes technology, urbanism and modernism, distinct from and often destructive of wildlife and nature.

But wildlife contraception is a practical solution to the problems that often arise where people and wildlife intersect at messy physical and category boundaries.

Among the creatures that cross boundaries are bison, which regularly breach government-drawn lines while bearing a split cultural identity as both wildlife and livestock; wild horses which, depending on your perspective, may be wildlife, or livestock, or nuisances, or pets; and deer, whose cultural identity becomes clouded when they leave the hills of Colorado’s Front Range or western Pennsylvania and proliferate in Philadelphia parks, on the outskirts of Chicago, or in the city limits of Boulder or Helena.

Those messy boundaries are spreading. So here’s my advice: Open a mental file, label it “wildlife contraception,” and start learning about it. You’ll soon discover just why it’s a very good idea.

Allen Rutberg is a contributor to Writers on the Range, a column service of High Country News. He is director of the Center for Animals and Public Policy, Cummings School of Veterinary Medicine at Tufts University, North Grafton, Massachusetts.

Note: the opinions expressed in this column are those of the writer and do not necessarily reflect those of High Country News, its board or staff. If you'd like to share an opinion piece of your own, please write Betsy Marston at [email protected].

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